Peep sight for furnaces



March 22, 1938. .1t BUZARD y 2,112,063

PEEP SIGHT FOR FURNACES Filed Aug. 7. 1956 Patented Mar. 22, 1938lm'raN'rl OFFICE PEEP SIGHT FOR FURNACES John Blizard, Garden City, N.Y., assignor to Foster Wheeler Corporation, New York, N. Y., acorporation of New York Application August 7, 1936, Serial No. 94,751

is ci. (ci. 126-190) My invention relates to furnaces, and an improvedmeans for permitting observation of internal furnace conditions, and theaction of the vburning gases on the refractory walls of a hightemperature furnace chamber,` and on any .tubes or other devicesdisposed therein.

The invention is particularly applicable to furnaces which are wholly orpartially surrounded by an air duct or air chamber, in which thepressure is higher than that existing in the fur- I nace, and in whichan aperture or peephole of special design, comprising a sight tube andnozzle member, opens to the atmosphere in the boiler room or ring isleand extends inwardly `therefrom through the air duct and refractory'furnace Wall to the furnace, whereby a clear vision may be had into thefurnace chamber whenever desired, without discomfort or injury andwithout the use of any interposed transparent material such as glass ormica.

In operation, such devices depend on the pressure differential existingbetween the air duct and the furnace to create a flow of air from theair duct of sumcientA momentum to oppose any flow of gases from thefurnace, and further depend upon a Venturi shaped nozzle assembly anddiffuser to force the air from the air duct through the peephole intothe furnace at the desired velocity. Apparatus of the kind described isbroad-` ly disclosed in, and forms the subject matter of the applicationof Hugh E. Carleton, Serial No. 89,287, filed July 7, 2,105,309, grantedJanuary 11, 1938.

The present invention constitutes an improvement thereon, and includes adamper for shutting .olf the ow of air from the air duct to the furnaceduring the periods when visual access to the furnace is not desired,which is highly desirable from the standpoint of combustion. Also, thearrangement is such that the opening to the peephole in the boiler roomor ring isle cannot be opened for'use until after the damper has beenmoved to the fully open position, thus first establishing a ow of airduct into the furnace and preventing possible injury to the operatingpersonnel by an outward blast of furnace gases or preheated air, whichwould be'the result if the order of the operation were reversed, due tothe relatively high pressure existing in the air.

l duct and furnace chamber.

1936,` now Patent No.v

Fig. 1 is a vertical sectional view of `a preferred form of apparatusembodying the invention, taken substantially on line I--I 'of Fig. 2;

Fig.A 2 is an elevation of the outer end of the apparatus, as shown inFig. 1; and 5 Fig. 3 is a transverse sectional view of the apparatustaken on line l:i3- 3 of Fig. 1.

Like reference characters refer to like parts throughout the severalviews..

Referring to the drawing, particularly Fig. l, 10 reference character l0designates the inner refractory lining of a furnace chamber having anouter lining of suitable refractory material, while I2 and I2' indicatethe inner metallic casing walls of an air duct or chamber I3 which mayl5 entirely surround the furnace or may be disposed on and exteriorlyof, one or more walls thereof. 'I'he outer wall is formed by heatinsulating material designated I4 and outer metallic casing I5. Suitablemeans are provided to maintain a pres- 20 sure in the air chamber whichis higher `than the pressure in the furnace, or that yof the surround- 4ing atmosphere.

The. peephole arrangement selected for illustration, includes a taperedsight tube I6 having an inner end portion I6' and a laterally extendingannular ange at its outer end. The inner end of the sight tube extendsinto the throat or reduced portion 25 of a nozzle member 23 which issecured by bolts 24 and 24 to casing I2, and-30 forms in combinationwith an enlarged furnace opening 26, a Venturi shaped nozzle assemblyand diffuser which is arranged and adapted to provide when the peepholeis in use, the desired volume and velocity of air ow therethrough fromthe 35 air chamber to the furnace, and at the same time to permit a widerange of vision within the furnace when the sight tube cover plate I'Iis removed. If desired, the nozzle member 23 may be arranged to extendentirely through the fur- 40 nace wall, in which event a flared aperturein the furnace wall may not be necessary. Cover plate I'I, which opensto the boiler room or ring isle, is secured to an intermediate portionof a latch I8 by a pin I9, and the latch is hinged at 45 one end by pin20 on spaced studs 20' extending from the annular ange on the sight tubeI6. 'I'he other end of the latch I8 is provided with a slot I8 whichreceives a swinging bolt 2| secured to'said annular flange. As shown inthe drawing, 5 0 swinging bolt 2| also passes through a slot 3|' in a'lever arm 3| forming. a part of the damper means hereinafter described,and both the lever arm and the cover plate I1 are secured in closedposition by a wing nut 2| `threaded on the bolt 2|. 55

'I'he lsight tube I8 is supported on the outer wall of the air chamberby means of the annular flange thereon and by bolts 22 that pass throughthe ange and the outer wall.

Reference character 21 designates a thin, generally triangular orsegmental shaped metal disc, or damper, fixed to squareddlportion 84 ofan operating shaft 28 by washers 35 and nuts Il and 31. The cylindricalinner end 20 of shaft 28 is supported by bearing block 38 and rotatestherein. while the outer end Iii passes through the annular flangedportion of sight tube IB and is supported thereby for rotation in gland40. Air leakage through the gland is prevented by packing 39. The leverarm 3i is iixed to operating shaft 28 by cap screw 33 and is operated byhandle 32. The damper 21 is received by a narrow transverse slot orgroove 42 disposed in the nozzle member 23 inwardly of the inner end I6'of sight tube I 6, and is adapted for a limited rotary movement thereinwhen operated by shaft 28 and lever arm 3|. An orifice 4| in damper 21corresponds substantially in diameter to the diameter of the throat ofthe nozzle member. The arrangement is such that by rotating the damperthrough a relatively small arc or range, transversely to the axis of thenozzle member, either the ow of air to the furnace can be entirely cutoff, or the orifice 4I can be brought in axial alignment or registerwith the throat of the nozzle member, and a flow of air established fromthe air duct to the furnace. When .in the fully open position, asindicated by position A of the damper in Fig. 2 of the drawing, stop nut43 on damper 21 is in contact with the outer wall of the nozzle member,thereby preventing movement of the damper beyond fully open position.

As illustrated in the drawing, the damper is closed, and all flow fromthe air duct to the fur-f nace is cut oil'; both the lever arm 3i andcover plate I1 of the sight tube are securely held in closed positionby, latch I 8, swinging bolt 2| and wing nut 2| threaded thereon. ,Whenit is desired to use the peephole, wing nut 2l' is loosened and thelever arm 3| is moved upwardly to the right, as shown by dot and dashlines in Fig. 2, until further movement is prevented by the stop nut 43,in which position the lever will be clear of the cover plate. 'I'he bolt2| is then swung free of the latch i8, and the latch and the cover plateare swung downwardly away from the outer end of the sight tube, thuspermitting a clear vision through the peephole to the furnace withoutdiscomfort or risk of injury due to a sudden blast of hot air or furnacegases. When it is no plonger desired to use the peephole, the damper ismoved to closed position and the several parts associated therewith arereturned to the positions shown in the drawing.

Itis to be understood that changes may be made in the form and structureof the apparatus herein described and disclosed, without departing fromthe principles of the invention which is not to be limited except by thescope of the appended claims.

What I claim is:

1. In a furnace having an air chamber outside at least one wall thereof,means for observing combustion and internal furnace conditionscomprising a sight tube, a nozzle member arranged to conduct air fromthe air chamber to the furnace and cooperating with the sight tube insuch manner as to permit observation of the furnace interior through thesight tube and nozzlelmember, and a shut-off damper for the nozzlemember movable transversely of the axis of the nozzle member.

2. In a furnace wholly or partially surrounded by an air chamber, apeephole assembly comprising a nozzle member extending between the airchamber and the furnace, a sight tube extending through the wall of theair chamber inwardly to the throat of the nozzle member, and a damperfor the nozzle member disposed inwardly of the furnace end of said sighttube for controlling the iiow of air through the nozzle member from saidair chamber to the furnace.

3. In a furnace having an air chamber outside at least one wall thereof,means for observing combustion and internal furnace conditions therein,comprising a nozzle member for conducting air from the air chamber tothe furnace. a sight tube extending through the outer wall of the airchamber and cooperating with lthe nozzle member, a cover for the outerend of the sight tube, and a damper for the nozzle member operableindependently of the sight tube and its cover.

4. In a furnace having an air chamber outside at least one wail thereof,means for observing combustion and internal furnace conditions therein,comprising a 'nozzle member Yfor conducting air from the airchamber tothe furnace, a sight tube extending through the outer wall of the airchamber and cooperating with the nozzle member, a cover for the outerend of the sight tube, a damper for the nozzle member, and meansindependent of the sight tube and its cover "or operating the damper,said damper operating means being disposed so as to prevent movement ofthe sight tube cover to open pojtun when the damper is in closedposition.

5. In a furnace having an air chamber outside at least one wall thereof,means for observing combustion and internal furnace conditions therein,comprising a nozzle member for conducting air from the air chamber tothe furnace, a sight tube extending through the outer wall of the airchamber and cooperating with the nozzle member, a cover for the outerend of the sight tube, a damper for the nozzle member, means independentof the sight tube and its cover for operating the. damper, and singlemeans for v securing the damper and said cover in closed position.

end of said sight tube, and a damper for saidv nozzle member movabletransversely of the axis of said nozzle member for controlling the flowof air therethrough, and common means for securing said cover plate andsaid damper in closed position.

'1. In a furnace having an air chamber outside at least one wallthereof, a peephole for observing internal furnace conditions comprisinga nozzle member arranged to conduct air from the air chamber to thefurnace, a sight tube in axial augment with the nozzle member, a coverplate for the outer end of said sight tube, a damper for said nozzlemember disposed inwardly of the furnace end of said sight tube, andcommon means for securing said cover plate and damper in closedposition.

8. In a furnace having an air chamber outside anaoea at least one wallthereof, a peephole for observing internal furnace conditions comprisinga nozzle member arrangedy to conduct air from the air chamber to thefurnace, a sight tuberextending through the wall of the `air chamber tothe throat of the nozzle member, a cover plate for closing said sighttube, a damper for said nozzle member movable transversely of the axisthereof for controlling the flow of air therethrough, a lever foropening and closing said damper, and common means for securing both thedamper and cover plate in closed position, the arrangement v being suchas to prevent the opening of said cover `plate when said damper isclosed. l

9. In a furnace having an air chamber outside y at least one wallthereof, a peephole for observing internal furnace conditions comprisinga nozzle member arranged to conduct air from the air chamber to thefurnace, a sight tube extending through the wall of the air chamber tothe throat of the nozzle member, a cover plate for closing said sighttube, a damper for said nozzle member, an orice in the damper, and meansfor rotating said damper transversely of the axis of said nozzle memberwhereby the orice is moved into or out of alignment with the nozzlemember, thereby permitting or preventingilow of air through the nozzlemember from said air chamber to the furnace. l

10. In a furnace having an air chamber outside at least one wallthereof, a peephole for observing internal furnace conditions comprisingya nozzle memberarranged to conduct air from the air chamber to thefurnace, a sight tube extending through the wall of the air chamber tothe throat of the nozzle member, a cover plate for closing the sighttube, a damper for said nozzle member disposed inwardly of the furnaceend of said sight tube. an orifice in the damper having a flow areasubstantially equal to the ilow area of the-throat of the nozzle member,means for rotating said damper through a limited arc to open or closesaid nozzle member, and common means for securing the cover plate anddamper in closed position, said means for rotating the damper beingarranged and disposed so as to prevent the opening of said cover platebefore said damper has been rotated to the fully open position.

11. In a furnace having an air chamber outside at least one wallthereof, a peephole for observing internal furnace conditions comprisinga nozzle member arranged to conduct air from the air chamber to thefurnace. a sight tube extending through the wall of the air chamber tothe throat of said nozzle member, a cover plate for closing said sighttube, a damper for the nozzle member disposed inwardly of the furnaceend of said sight tube, a shaft extending through the wall of the airchamber and operably connected to the damper, an operating lever xed tothe shaft at its outer end and arranged lto overlap said cover4 plate,and common means for securingthe lever and cover plate in closedposition, the arrangement being such that said cover plate cannot beremoved from said sight tube until the damper is moved to a position invwhich the nozzle member is open.

l2. In a furnace having an air duct outside at least one wall thereof,means for observing combustion and internal furnace conditionscomprising a nozzle in a wall of the furnace, a sight tube extendingthrough the wall of the air duct and having its inner end so disposedwith respect to the nozzle that uid ow through the latter causes airflow inwardly through the tube, and a shut off damper for the nozzlemember movable transversely of the axis of the nozzle member.

13. In a furnace having an air duct outside at least one wall thereof,means for observing combustion and internal furnace conditionscomprising a nozzle in a wall of the furnace, a sight tube

